This invention relates to an accompaniment generation system for automatically generating an accompaniment line supporting a melody tone and more particularly to a system for determining principal tones of such an acompaniment line.
Technology for automatically generating an accompaniment line such as a bass line or an obbligato line was known. This kind of technique has been developed in the field of electronic musical instruments, and it is incorporated as an automatic accompaniment function of electronic musical instruments. In the prior art automatic accompaniment generation systems, roots are used as principal tones of the accompaniment line. In real-time systems, the source of roots is provided from a music input device such as a keyboard. For example, a certain area of a keyboard is allotted to a chord input key region, and the type and root of each chord is determined from key data input from the key region. Each determined root is used as an accompaniment line principal tone, and an accompaniment pattern is produced on the basis of such a principal tone. The automatic accompaniment line generation techniques are also applicable to nonreal-time type systems. In the nonreal-time type systems, chord progression data is stored in a memory. In operation, chord data is read out for each chord time interval or segment, and the root of each chord constitutes a principal tone of the accompaniment pattern.
The problem of the root approach noted above is that since each principal tone fundamental to the accompaniment line is a root at all time, the line is very poor in variety.
In this viewpoint, the applicant has filed patent applications for a system for automatically generating an accompaniment line in a different approach (Japanese Laid Open Patent Application Sho 62-67593, Japanese Laid-Open Patent Application Sho 62-67594, both of which were filed on Sept. 9, 1985 under a title of "Electronic Musical Instrument with Automatic Accompaniment Function"). In the system according to these applications, an adjacent or proximate tone progression is used in lieu of a root progression. More particularly, the automatic accompaniment line generation function has an adjacent tone logic, in which a tone closest to the immediately preceding accompaniment tone among the current chord members is determined to be a current accompaniment tone. Further, Japanese Patent Application Sho 60-207175 shows an improved logic for forming an accompaniment line with adjacent tones moving opposite to a bass line. The adjacent tone logic noted above guarantees that the tone other than the root can be a principal tone. Further, the improvement logic is a contrapuntal or counterpoint approach and is useful for generation of a line with a vivid movement.
However, compared to an accompaniment performance by an excellent player there still remains much room for improvement. One of the features of accompaniment by a human composer or performer is to generate a line in conformity to "musical situation". In the prior art automatic accompaniment line generation techniques, only insufficient considerations are paid to these points.